Contact structure and production method thereof

ABSTRACT

A contact structure for establishing electrical contact with contact targets. The contact structure is formed of a contact substrate and a plurality of contactors in which each of the contactors has a hook shape. The contactor has a tip portion which is protruded in a vertical direction to form a contact point, a base portion which is inserted in a through hole provided on the contact substrate in such a way that an end of the contactor functions as a contact pad for electrical connection at a bottom surface of the contact substrate, and a curved portion provided between the tip portion and the base portion which produces a contact force when the contactor is pressed against the contact target. A further aspect is a method for producing a large number of contactors on a wafer in a horizonal direction and removing the contactors from the wafer to be mounted on a substrate to form the contact structure such as a probe card, IC chip, or other contact mechanism in a vertical direction.

FIELD OF THE INVENTION

[0001] This invention relates to a contact structure and its productionmethod, and more particularly, to a contact structure having a largenumber of contactors in a vertical direction and to a method forproducing such a large number of contactors on a semiconductor wafer ina horizonal direction and removing the contactors from the wafer to bemounted on a substrate in a vertical direction to form the contactstructure such as a probe card, IC chip, or other contact mechanism in avertical direction.

BACKGROUND OF THE INVENTION

[0002] In testing high density and high speed electrical devices such asLSI and VLSI circuits, a high performance contact structure such as aprobe card having a large number of contactors must be used. In otherapplications, contact structures may be used for IC packages as ICleads. The present invention is directed to a production process of suchcontact structures to be used in testing LSI and VLSI chips,semiconductor wafers, burn-in of semiconductor wafers and die, testingand burn-in of packaged semiconductor devices, printed circuit boardsand the like. The present invention can also be applicable to otherpurposes such as forming leads or terminal pins of IC chips, IC packagesor other electronic devices. However, for the convenience ofexplanation, the present invention is described mainly with reference tothe semiconductor wafer testing.

[0003] In the case where semiconductor devices to be tested are in theform of a semiconductor wafer, a semiconductor test system such as an ICtester is usually connected to a substrate handler, such as an automaticwafer prober, to automatically test the semiconductor wafer. Such anexample is shown in FIG. 1 in which a semiconductor test system has atest head 100 which is ordinarily in a separate housing and electricallyconnected to the test system with a bundle of cables 110. The test head100 and a substrate handler 400 are mechanically as well as electricallyconnected with one another with the aid of a manipulator 500 which isdriven by a motor 510. The semiconductor wafers to be tested areautomatically provided to a test position of the test head 100 by thesubstrate handler 400.

[0004] On the test head 100, the semiconductor wafer to be tested isprovided with test signals generated by the semiconductor test system.The resultant output signals from the semiconductor wafer under test (ICcircuits formed on the semiconductor wafer) are transmitted to thesemiconductor test system. In the semiconductor test system, the outputsignals are compared with expected data to determine whether the ICcircuits on the semiconductor wafer function correctly.

[0005] In FIG. 1, the test head 100 and the substrate handler 400 areconnected through an interface component 140 consisting of a performanceboard 120 (shown in FIG. 2) which is a printed circuit board havingelectric circuit connections unique to a test head's electricalfootprint, coaxial cables, pogo-pins and connectors. In FIG. 2, the testhead 100 includes a large number of printed circuit boards 150 whichcorrespond to the number of test channels (test pins) of thesemiconductor test system. Each of the printed circuit boards 150 has aconnector 160 to receive a corresponding contact terminal 121 of theperformance board 120. A “frog” ring 130 is mounted on the performanceboard 120 to accurately determine the contact position relative to thesubstrate handler 400. The frog ring 130 has a large number of contactpins 141, such as ZIF connectors or pogo-pins, connected to contactterminals 121, through coaxial cables 124.

[0006] As shown in FIG. 2, the test head 100 is placed over thesubstrate handler 400 and mechanically and electrically connected to thesubstrate handler through the interface component 140. In the substratehandler 400, a semiconductor wafer 300 to be tested is mounted on achuck 180. In this example, a probe card 170 is provided above thesemiconductor wafer 300 to be tested. The probe card 170 has a largenumber of probe contactors (such as cantilevers or needles) 190 tocontact with contact targets such as circuit terminals or contact padsin the IC circuit on the semiconductor wafer 300 under test.

[0007] Electrical terminals or contact receptacles (contact pads) of theprobe card 170 are electrically connected to the contact pins 141provided on the frog ring 130. The contact pins 141 are also connectedto the contact terminals 121 of the performance board 120 with thecoaxial cables 124 where each contact terminal 121 is connected to theprinted circuit board 150 of the test head 100. Further, the printedcircuit boards 150 are connected to the semiconductor test systemthrough the cable 110 having, for example, several hundreds of innercables.

[0008] Under this arrangement, the probe contactors 190 contact thesurface (contact targets) of the semiconductor wafer 300 on the chuck180 to apply test signals to the semiconductor wafer 300 and receive theresultant output signals from the wafer 300. The resultant outputsignals from the semiconductor wafer 300 under test are compared withthe expected data generated by the semiconductor test system todetermine whether the IC circuits on the semiconductor wafer 300performs properly.

[0009]FIG. 3 is a bottom view of the probe card 170 of FIG. 2. In thisexample, the probe card 170 has an epoxy ring on which a plurality ofprobe contactors 190 called needles or cantilevers are mounted. When thechuck 180 mounting the semiconductor wafer 300 moves upward in FIG. 2,the tips of the cantilevers 190 contact the pads or bumps (contacttargets) on the wafer 300. The ends of the cantilevers 190 are connectedto wires 194 which are further connected to transmission lines (notshown) formed in the probe card 170. The transmission lines areconnected to a plurality of electrodes (contact pads) 197 which are incommunication with the pogo pins 141 of FIG. 2.

[0010] Typically, the probe card 170 is structured by a multilayer ofpolyimide substrates having ground planes, power planes, signaltransmission lines on many layers. As is well known in the art, each ofthe signal transmission lines is designed to have a characteristicimpedance such as 50 ohms by balancing the distributed parameters, i.e.,dielectric constant and magnetic permeability of the polyimide,inductances and capacitances of the signal paths within the probe card170. Thus, the signal lines are impedance matched lines establishing ahigh frequency transmission bandwidth to the wafer 300 for supplyingcurrents in a steady state as well as high current peaks generated bythe device's outputs switching in a transient state. For removing noise,capacitors 193 and 195 are provided on the probe card between the powerand ground planes.

[0011] An equivalent circuit of the probe card 170 is shown in FIG. 4 toexplain the limitation of the high frequency performance in theconventional probe card technology. As shown in FIGS. 4A and 4B, thesignal transmission line on the probe card 170 extends from theelectrode 197, the strip (impedance matched) line 196, the wire 194 andthe needle or cantilever (contact structure) 190. Since the wire 194 andneedle 190 are not impedance matched, these portions function as aninductor L in the high frequency band as shown in FIG. 4C. Because ofthe overall length of the wire 194 and needle 190 is around 20-30 mm,significant limitations will be resulted from the inductor when testinga high frequency performance of a device under test.

[0012] Other factors which limit the frequency bandwidth in the probecard 170 reside in the power and ground needles shown in FIGS. 4D and4E. If the power line can provide large enough currents to the deviceunder test, it will not seriously limit the operational bandwidth intesting the device. However, because the series connected wire 194 andneedle 190 for supplying the power (FIG. 4D) as well as the seriesconnected wire 194 and needle 190 for grounding the power and signals(FIG. 4E) are equivalent to inductors, the high speed current flow isseriously restricted.

[0013] Moreover, the capacitors 193 and 195 are provided between thepower line and the ground line to secure a proper performance of thedevice under test by filtering out the noise or surge pulses on thepower lines. The capacitors 193 have a relatively large value such as 10μF and can be disconnected from the power lines by switches ifnecessary. The capacitors 195 have a relatively small capacitance valuesuch as 0.01 μF and fixedly connected close to the DUT. These capacitorsserve the function as high frequency decoupling on the power lines. Inother words, the capacitors limit the high frequency performance of theprobe contactor.

[0014] Accordingly, the most widely used probe contactors as noted aboveare limited to the frequency bandwidth of approximately 200 MHz which isinsufficient to test recent semiconductor devices. In the industry, itis considered that the frequency bandwidth comparable to the tester'scapability, which is currently on the order of 1 GHz or higher, will benecessary in the near future. Further, it is desired in the industrythat a probe card is capable of handling a large number of semiconductordevices, especially memories, such as 32 or more, in a parallel fashionto increase test throughput.

[0015] In the conventional technology, the probe card and probecontactors such as shown in FIG. 3 are manually made, resulting ininconsistent quality. Such inconsistent quality includes fluctuations ofsize, frequency bandwidth, contact forces and resistance, etc. In theconventional probe contactors, another factor making the contactperformance unreliable is a temperature change under which the probecontactors and the semiconductor wafer under test have differenttemperature expansion ratios. Thus, under the varying temperature, thecontact positions therebetween vary which adversely affects the contactforce, contact resistance and bandwidth. Thus, there is a need of acontact structure with a new concept which can satisfy the requirementin the next generation semiconductor test technology.

SUMMARY OF THE INVENTION

[0016] Therefore, it is an object of the present invention to provide acontact structure having a large number of contactors for electricallycontacting contact targets with a high frequency bandwidth, high pincounts and high contact performance as well as high reliability.

[0017] It is another object of the present invention to provide acontact structure such as a probe card to establish electricalconnection for testing semiconductor devices and the like, having a veryhigh frequency bandwidth to meet the test requirements in the nextgeneration semiconductor test technology.

[0018] It is a further object of the present invention to provide acontact structure to establish electrical connection in applicationssuch as testing semiconductor devices, which are suitable for testing alarge number of semiconductor devices in parallel at the same time.

[0019] It is a further object of the present invention to provide amethod for producing a large number of contactors by using relativelysimple technique.

[0020] It is a further object of the present invention to provide amethod for producing a large number of contactors in a two dimensionalmanner rather than a three dimensional manner on a planar surface of asilicon substrate.

[0021] It is a further object of the present invention to provide amethod for producing a large number of contactors in a two dimensionalmanner on a silicon substrate, removing the contactors from thesubstrate and mounting the contactors on a contact substrate in a threedimensional manner to form a contact structure.

[0022] It is a further object of the present invention to provide amethod for producing a large number of contactors in a two dimensionalmanner on a silicon substrate, transferring the contactors to anadhesive tape and removing the contactors therefrom for verticallymounting them on a contact substrate to forma a contact structure.

[0023] It is a further object of the present invention to provide amethod for producing a large number of contactors with low cost and highefficiency and reliability.

[0024] In the present invention, a contact structure for testing(including burn-in) a semiconductor wafers, packaged LSIs or printedcircuit boards (devices under test) are formed of a large number ofcontactors produced on a planar surface of a silicon substrate by aphotolithography technology established in the semiconductor productionprocess. The contact structure of the present invention can also be usedas components of electronics devices such as IC leads and pins.

[0025] The first aspect of the present invention is a contact structurefor establishing electrical connection with contact targets. The contactstructure is formed of a contact substrate and a plurality of contactorsin which each of the contactors has a hook shape. The hook shapecontactor is comprised of a tip portion which is protruded in a verticaldirection to form a contact point, a base portion which is inserted in athrough hole provided on the contact substrate in such a way that an endof the contactor functions as a contact pad for electrical connection ata bottom surface of the contact substrate, and a curved portion providedbetween the tip portion and the base portion which produces a contactforce when the contactor is pressed against the contact target.

[0026] In another aspect of the contact structure of the presentinvention, the contact structure is formed of a contact substrate and aplurality of contactors in which each of the contactors has a loopshape. The loop shape contactor is comprised of a center portion whichis protruded in a vertical direction to form a contact point, a baseportion having two ends which are inserted in through holes provided onthe contact substrate in such a way that at least one end of thecontactor is projected from a bottom surface of the contact substrate tofunction as a contact pad, a curved portion between the tip portion andthe base portion to produce a contact force when the contactor ispressed against the contact target.

[0027] Another aspect of the present invention is a method of producingthe contactors in a two dimensional manner on a silicon substrate andremoving therefrom for establishing a contact structure. The productionmethod is comprised of the following steps of:

[0028] (a) forming a sacrificial layer on a surface of a siliconsubstrate;

[0029] (b) forming an conductive layer made of electric conductivematerial on the sacrificial layer;

[0030] (c) forming a photoresist layer on the conductive layer;

[0031] (d) aligning a photo mask over the photoresist layer and exposingthe photoresist layer with ultraviolet light through the photo mask, thephoto mask including an image of the contactors;

[0032] (e) developing patterns of the image of the contactors on asurface of the photoresist layer;

[0033] (f) forming the contactors made of electric conductive materialin the patterns on the photoresist layer by an electroplating process;

[0034] (g) stripping the photoresist layer;

[0035] (h) removing the sacrificial layer and the conductive layer by anetching process so that the contactors are separated from the siliconsubstrate; and

[0036] (i) mounting the contactors on a contact substrate having throughholes to receive ends of the contactors therein so that at least one endof each of the contactors functions as a contact pad for electricconnection.

[0037] A further aspect of the present invention is another method ofproducing the contactors in a two dimensional manner on a siliconsubstrate and transferring the contactors to the adhesive tape andremoving therefrom for establishing a contact structure. The productionmethod is comprised of the following steps of:

[0038] (a) forming a sacrificial layer on a surface of a siliconsubstrate;

[0039] (b) forming an conductive layer made of electric conductivematerial on the sacrificial layer;

[0040] (c) forming a photoresist layer on the conductive layer;

[0041] (d) aligning a photo mask over the photoresist layer and exposingthe photoresist layer with ultraviolet light through the photo mask, thephoto mask including an image of the contactors;

[0042] (e) developing patterns of the image of the contactors on asurface of the photoresist layer;

[0043] (f) forming the contactors made of electric conductive materialin the patterns on the photoresist layer by an electroplating process;

[0044] (g) stripping the photoresist layer;

[0045] (h) placing an adhesive tape on the contactors so that uppersurfaces of the contactors adhere to the adhesive tape;

[0046] (i) removing the sacrificial layer and conductive layer by anetching process so that the contactors on the adhesive tape areseparated from the silicon substrate; and

[0047] (j) mounting the contactors on a contact substrate having throughholes to receive therein ends of the contactors wherein at least one endof each of the contactors function as a pad for electric connection.

[0048] A further aspect of the present invention is a method ofproducing the contactors in a two dimensional manner on a siliconsubstrate and transferring the contactors to the adhesive tape. Theproduction method is comprised of the following steps of:

[0049] (a) forming an conductive substrate made of electric conductivematerial on a dielectric substrate;

[0050] (b) forming a photoresist layer on the conductive substrate;

[0051] (c) aligning a photo mask over the photoresist layer and exposingthe photoresist layer with ultraviolet light through the photo mask, thephoto mask including an image of the contactors;

[0052] (d) developing patterns of the image of the contactors on asurface of the photoresist layer;

[0053] (e) forming the contactors made of electric conductive materialin the patterns on the photoresist layer by an electroplating process;

[0054] (f) stripping off the photoresist layer;

[0055] (g) peeling the conductive substrate having contactors thereonfrom the dielectric substrate;

[0056] (h) placing an adhesive tape on the contactors on the conductivesubstrate so that upper surfaces of the contactors adhere to theadhesive tape wherein adhesive strength between the contactor and theadhesive tape is larger than that between the contactor and theconductive substrate;

[0057] (i) peeling the conductive substrate so that the contactors onthe adhesive tape are separated from the conductive substrate; and

[0058] (j) mounting the contactor on a contact substrate having athrough hole in such a way the an end of the contactor is projected froman opposite surface of the contact substrate.

[0059] A further aspect of the second present invention is a process ofproducing a contact structure having the above noted contactors with useof a pick and place mechanism. The production process is comprised ofthe following steps of:

[0060] (a) forming a sacrificial layer on a surface of a siliconsubstrate;

[0061] (b) forming an conductive layer made of electric conductivematerial on the sacrificial layer;

[0062] (c) forming the contactors through a photolithography process,the contact structures being in a horizontal directions on the siliconsubstrate;

[0063] (d) transferring the contactors from the silicon substrate to anadhesive tape;

[0064] (e) positioning the adhesive tape having the contactors in aspecified location;

[0065] (f) picking the contactor from the adhesive tape and orientingthe contactor in a predetermined direction;

[0066] (g) positioning a contact substrate having through holes forreceiving therein base portions of the contactors; and

[0067] (h) placing the contactors on predetermined positions of thecontact substrate by inserting ends of the contactors in such a way thatat least one end of each of the contactors functions as a contact padfor electrical connection.

[0068] According to the present invention, the contact structure has avery high frequency bandwidth to meet the test requirements of nextgeneration semiconductor technology. Since the large number ofcontactors are produced at the same time on the substrate withoutinvolving manual handling, it is possible to achieve consistent quality,high reliability and long life in the contact performance as well as lowcost. Further, because the contactors are assembled on the samesubstrate material as that of the device under test, it is possible tocompensate positional errors caused by temperature changes.

[0069] Further, according to the present invention, the productionprocess is able to produce a large number of contactors in a horizontaldirection on the silicon substrate by using relatively simple technique.Such contactors produced are removed from the substrate and mounted on acontact substrate in a vertical direction. The contactors produced bythe present invention are low cost and high efficiency and have highmechanical strength and reliability. The contact structure of thepresent invention are advantageously applied in testing a semiconductorwafer, packaged LSI, multi-chip module and the like including burn-intesting.

BRIEF DESCRIPTION OF THE DRAWINGS

[0070]FIG. 1 is a schematic diagram showing a structural relationshipbetween a substrate handler and a semiconductor test system having atest head.

[0071]FIG. 2 is a diagram showing an example of a more detailedstructure for connecting the test head of the semiconductor test systemto the substrate handler through an interface component.

[0072]FIG. 3 is a bottom view showing an example of the probe cardhaving an epoxy ring for mounting a plurality of probe contactors(needles or cantilevers) in the conventional technology.

[0073] FIGS. 4A-4E are circuit diagrams showing equivalent circuits ofthe probe card of FIG. 3.

[0074]FIG. 5 is a schematic diagram showing an example of contactstructure of the present invention using contactors produced in ahorizontal direction on a surface of a silicon substrate where each ofthe contactor has a hook shape.

[0075]FIG. 6 is a schematic diagram showing another example of contactstructure of the present invention using contactors produced in ahorizontal direction on a surface of a silicon substrate where each ofthe contactor has a loop shape.

[0076] FIGS. 7A-7D are schematic diagrams showing basic concepts ofproduction method of the present invention in which a large number ofcontactors are formed on a planar surface of a silicon substrate andremoved therefrom for later processes.

[0077] FIGS. 8A-8L are schematic diagrams showing an example ofproduction process in the present invention for producing thecontactors.

[0078] FIGS. 9A-9D are schematic diagrams showing another example ofproduction process in the present invention for producing thecontactors.

[0079] FIGS. 10A-10N are schematic diagrams showing another example ofproduction process in the present invention for producing thecontactors.

[0080]FIGS. 11A and 11B are schematic diagrams showing an example ofpick and place mechanism and its process for picking the contactors andplacing the same on a substrate such as a multi-layered siliconsubstrate to produce the contact structure of the present invention.

[0081] FIGS. 12 is a schematic diagram showing an example of contactstructure of the present invention having a multi-layered siliconsubstrate and contactors produced through the production process of thepresent invention where each of the contactor has a hook shape.

[0082] FIGS. 13 is a schematic diagram showing an example of contactstructure of the present invention having a multilayered siliconsubstrate and contactors produced through the production process of thepresent invention where each of the contactor has a loop shape.

[0083]FIG. 14 is a perspective view showing an example of contactstructure of the present invention having a large number of contactorsproduced through the processes of the present invention.

[0084]FIG. 15 is a cross sectional view showing an example of totalstack-up structure using the contact structure of the present inventionas an interface between a semiconductor device under test and a testhead.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0085]FIGS. 5 and 6 show examples of contact structure of the presentinvention. Each contact structure is configured by a contact substrate20 and contactors 30. In the example of FIG. 5, each contactor 30 ₁ hasa hook shape and formed of a base portion which is connected to thecontact substrate 20, a contact point which is preferably sharpened andoriented in a vertical direction, and a horizontally curved portionbetween the base portion and the contact point. In the example of FIG.6, each contactor 302 has a loop like shape is formed of a base portionhaving two ends connected to the contact substrate 20, a loop likeportion which is horizontally curved, and a contact point provided atthe center of the loop like portion and protruded therefrom in avertical direction.

[0086] Each of the contactors 30 of FIGS. 5 and 6 produces contactpressure by a spring force derived mainly from the horizontally curvedportion when the contact structure is pressed against contact pads 320on the printed circuit board 300. The contact pressure also creates ascrubbing effect at the tip of the contactor against the surface ofcontact pad 320. Such a scrubbing effect promotes an improved contactperformance when the contact point scrubs the oxide surface of thecontact pad 320 to electrically contact the conductive material of thecontact pad 320. It should be noted that, in the present invention, thecontactors 30 ₁ and 30 ₂ are interchangeably used and produced althoughthe contact structure and its production method will be described withrespect to one of the contactors.

[0087]FIG. 7A-7D show basic ideas of the present invention for producingsuch contactors. In the present invention, as shown in FIG. 7A,contactors 30 ₂ are produced on a planar surface of a silicon substrate40 or other dielectric substrate in a horizontal direction, i.e., in atwo dimensional manner. Then, in the first example, as shown in FIG. 7B,the contactors 30 ₂ are removed from the silicon substrate 40 to bemounted on a contact substrate 20 of FIG. 6 such as a printed circuitboard, IC chip, or other contact mechanism in a vertical direction,i.e., in a three dimensional manner.

[0088] In the second example, as shown in FIG. 7C which is the same asFIG. 7A, contactors 30 ₁ are produced on a planar surface of a siliconor other dielectric substrate 40 in a horizontal direction, i.e., in atwo dimensional manner. Then, as shown in FIG. 7D, the contactors 30 ₁are transferred from the silicon substrate 40 to an adhesive member 90,such as an adhesive tape, adhesive film or adhesive plate (collectively“adhesive tape”). The contactors 30 ₁ on the adhesive tape are removedtherefrom to be mounted on a contact substrate 20 of FIG. 5 such as aprinted circuit board, IC chip, or other contact mechanism in a verticaldirection, i.e., in a three dimensional manner with use of a pick andplace mechanism.

[0089] FIGS. 8A-8L are schematic diagrams showing an example ofproduction process for producing the contactor 30 (30 ₁ or 30 ₂) in thefirst example (FIG. 7B) of the present invention where the adhesive tape90 is not involved in the production process. In FIG. 8A, a sacrificiallayer 42 is formed on a substrate 40 which is typically a siliconsubstrate. Other dielectric substrate is also feasible such as a glasssubstrate. The sacrificial layer 42 is made, for example, of silicondioxide (SiO₂) through a deposition process such as a chemical vapordeposition (CVD). The sacrificial layer 42 is to separate contactors 30from the silicon substrate in the later stage of the production process.

[0090] An adhesion promoter layer 44 is formed on the sacrificial layer42 as shown in FIG. 8B through, for example, an evaporation process. Anexample of material for the adhesioh promoter layer 44 includes chromium(Cr) and titanium (Ti) with a thickness of about 200-1,000 angstrom, forexample. The adhesion promoter layer 44 is to facilitate the adhesion ofconductive layer 46 of FIG. 8C on the silicon substrate 40. Theconductive layer 46 is made, for example, of copper (Cu) or nickel (Ni),with a thickness of about 1,000-5,000 angstrom, for example. Theconductive layer 46 is to establish electrical conductivity for anelectroplating process in the later stage.

[0091] In the next process, a photoresist layer 48 is formed on theconductive layer 46 over which a photo mask 50 is precisely aligned tobe exposed with ultraviolet (UV) light as shown in FIG. 8D. The photomask 50 shows a two dimensional image of the contactor 30 which will bedeveloped on the photoresist layer 48. As is well known in the art,positive as well as negative photoresist can be used for this purpose.If a positive acting resist is used, the photoresist covered by theopaque portions of the mask 50 harden (cure) after the exposure.Examples of photoresist material include Novolak(M-Cresol-formaldehyde), PMMA (Poly Methyl Methacrylate), SU-8 and photosensitive polyimide. In the development process, the exposed part of theresist can be dissolved and washed away, leaving a photoresist layer 48of FIG. 8E having an opening or pattern “A”. Thus, the top view of FIGS.8F(1) and 8F(2) show the pattern or opening “A” on the photoresist layer48 having the image (shape) of the contactor 30 ₁ or 30 ₂.

[0092] In the photolithography process in the foregoing, instead of theUV light, it is also possible to expose the photoresist layer 48 with anelectron beam or X-rays as is known in the art. Further, it is alsopossible to directly write the image of the contact structure on thephotoresist layer 48 by exposing the photoresist 48 with a direct writeelectron beam, X-ray or light source (laser).

[0093] The contactor material such as copper (Cu), nickel (Ni), aluminum(Al), rhodium (Rh), palladium (Pd), tungsten (W) or other metal;nickel-cobalt (NiCo) or other alloy combinations thereof is deposited(electroplated) in the pattern “A” of the photoresist layer 48 to formthe contactor 30 as shown in FIG. 8G. Preferably, a contact materialwhich is different from that of the conductive layer 46 should be usedto differentiate etching characteristics from one another as will bedescribed later. The over plated portion of the contactor 30 in FIG. 8Gis removed in the grinding (planarizing) process of FIG. 8H.

[0094] In the next process, the photoresist layer 48 is removed in aresist stripping process as shown in FIG. 8I. Typically, the resistlayer 48 is removed by wet chemical processing. Other examples ofstripping are acetone-based stripping and plasma O₂ stripping. In FIG.8J, the sacrificial layer 42 is etched away so that the contactor 30 isseparated from the silicon substrate 40. Another etching process isconducted so that the adhesion promoter layer 44 and the conductivelayer 46 are removed from the contactor 30 as shown in FIG. 8K.

[0095] The etching condition can be selected to etch the layers 44 and46 but not to etch the contactor 30. In other words, to etch theconductive layer 46 without etching the contactor 30, as noted above,the conductive material used for the contactor 30 must be different fromthe material of the conductive layer 46. Finally, the contactor 30 isseparated from any other materials as shown in the perspective view ofFIG. 8L. Although the production process in FIGS. 8A-8L shows only onecontactor 30, in an actual production process, as shown in FIGS. 7A-7D,a large number of contactors are produced at the same time.

[0096] FIGS. 9A-9D are schematic diagrams showing an example ofproduction process for producing the contactors in the second example(FIG. 7D) of the present invention. In the this example, an adhesivetape 90 is incorporated in the production process to transfer thecontactors 30 from the silicon substrate 40 to the adhesive tape. FIGS.9A-9D only show the latter part of the production process in which theadhesive tape 90 is-involved.

[0097]FIG. 9A shows a process which is equivalent to the process shownin FIG. 8I where the photoresist layer 48 is removed in the resiststripping process. Then, also in FIG. 9A, an adhesive tape 90 is placedon an upper surface of the contactor 30 so that the contactor 30 adheresto the adhesive tape 90. As noted above with reference to FIG. 7D,within the context of the present invention, the adhesive tape 90includes other types of adhesive member, such as an adhesive film andadhesive plate, and the like. The adhesive tape 90 also includes anymember which attracts the contactor 30 such as a magnetic plate or tape,an electrically charged plate or tape, and the like.

[0098] In the process shown in FIG. 9B, the sacrificial layer 42 isetched away so that the contactor 30 on the adhesive tape 90 isseparated from the silicon substrate 40. Another etching process isconducted so that the adhesion promoter layer 44 and the conductivelayer 46 are removed from the contactor 30 as shown in FIG. 9C.

[0099] As noted above, in order to etch the conductive layer 46 withoutetching the contactor 30, the conductive material used for the contactor30 must be different from the material of the conductive layer. Althoughthe production process in FIGS. 9A-9C shows only one contactor, in anactual production process, a large number of contactors are produced atthe same time. Thus, a large number of contactors 30 are transferred tothe adhesive tape 90 and separated from the silicon substrate and othermaterials as shown in the top view of FIG. 9D.

[0100] FIGS. 10A-10N are schematic diagrams showing a further example ofproduction process for producing the contactor 30 ₁ or 30 ₂ in thesecond example (FIG. 7D) where the contactors are transferred to theadhesive tape. In FIG. 10A, an electroplate seed (conductive) layer 342is formed on a substrate 340 which is typically a silicon or glasssubstrate. The seed layer 342 is made, for example, of copper (Cu) ornickel (Ni), with a thickness of about 1,000-5,000 angstrom, forexample. A chrome-inconel layer 344 is formed on the seed layer 342 asshown in FIG. 10B through, for example, a sputtering process.

[0101] In the next process in FIG. 10C, a conductive substrate 346 isformed on the chrome-inconel layer 344. The conductive substrate 346 ismade, for example, of nickel-cobalt (NiCo) with a thickness of about100-130 μm. After passivating the conductive substrate 346, aphotoresist layer 348 with a thickness of about 100-120 μm is formed onthe conductive substrate 346 in FIG. 10D and a photo mask 350 isprecisely aligned so that the photoresist layer 348 is exposed withultraviolet (UV) light as shown in FIG. 10E. The photo mask 350 shows atwo dimensional image of the contactor 30 which will be developed on thesurface of the photoresist layer 348.

[0102] In the development process, the exposed part of the resist can bedissolved and washed away, leaving a photoresist layer 348 of FIG. 10Fhaving a plating pattern transferred from the photo mask 350 having theimage (shape) of the contactor 30 (30 ₁ and/or 30 ₂). In the step ofFIG. 10G, contactor material is electroplated in the plating pattern onthe photoresist layer 348 with a thickness of about 50-60 μm. An exampleof the conductive material is nickel-cobalt (NiCo). The nickel-cobaltcontactor material will not strongly adhere to the conductive substrate346 made of nickel-cobalt.

[0103] In the next process, the photoresist layer 348 is removed in aresist stripping process as shown in FIG. 10H. In FIG. 10I, theconductive substrate 346 is peeled from the chrome-inconel layer 344 onthe substrate 340. The conductive substrate 346 is a thin, flexiblesubstrate on which the contactors 30 are mounted with a relatively weakadhesive strength. The top view of the conductive substrate 346 havingthe contactors 30 is shown in FIG. 10J.

[0104]FIG. 9A shows a process in which an adhesive tape 90 is placed onan upper surface of the contactors 30. The adhesive strength between theadhesive tape 90 and the contactors 30 is greater than that between thecontactors and the conductive substrate 346. Thus, when the adhesivetape 90 from the flexible conductive substrate 346, the contactors 30are transferred from the substrate 346 to the adhesive tape 90 as shownin FIG. 10L. FIG. 10M shows a top view of the adhesive tape 90 havingthe contactors 30 thereon and FIG. 10N is a cross sectional view of theadhesive tape 90 having the contactors 30 thereon.

[0105]FIGS. 11A and 11B are schematic diagrams showing an example ofprocess for picking the contactors 30 from the adhesive tape 90 andplacing the contactors on the contact substrate 20. The pick and placemechanism of FIGS. 11A and 11B is advantageously applied to thecontactors produced by the production process of the present inventiondescribed with reference to FIGS. 9A-9D and FIGS. 10A-10N involving theadhesive tape. FIG. 11A is a front view of the pick and place mechanism80 showing the first half process of the pick and place operation. FIG.11B is a front view of the pick and place mechanism 80 showing thesecond half process of the pick and place operation.

[0106] In this example, the pick and place mechanism 80 is comprised ofa transfer mechanism 84 to pick and place the contactors 30, mobile arms86 and 87 to allow movements of the transfer mechanism 84 in X, Y and Zdirections, tables 81 and 82 whose positions are adjustable in X, Y andZ directions, and a monitor camera 78 having, for example, a CCD imagesensor therein. The transfer mechanism 84 includes a suction arm 85 thatperforms suction (pick operation) and suction release (place operation)operations for the contactors 30. The suction force is created, forexample, by a negative pressure such as vacuum. The suction arm 85rotates in a predetermined angle such as 90 degrees.

[0107] In operation, the adhesive tape 90 having the contactors 30 andthe contact substrate 20 having the bonding locations 32 (or throughholes) are positioned on the respective tables 81 and 82 on the pick andplace mechanism 80. As shown in FIG. 11A, the transfer mechanism 80picks the contactor 30 from the adhesive tape 90 by suction force of thesuction arm 85. After picking the contactor 30, the suction arm 85rotates by 90 degrees, for example, as shown in FIG. 11B. Thus, theorientation of the contactor 30 is changed from the horizontal directionto the vertical direction. This orientation mechanism is just anexample, and a person skilled in the art knows that there are many waysto change the orientation of the contactors. The transfer mechanism 80then places the contactor 30 on the bonding location 32 (or throughholes) on the substrate 20. The contactor 30 is attached to the contactsubstrate 20 by being bonded to the surface or inserted in the throughholes.

[0108]FIG. 12 is a cross sectional view showing an example of contactstructure of the present invention using the contactors 301 producedthrough the process such as FIGS. 8A-8L, 9A-9D or 10A-10N. The contactor30 ₁ having the hook shape is attached to the contact substrate 20 in amanner that an end of the contactor 30 ₁ is inserted in a through hole25. In this example, the contact substrate 20 is a multi-layeredsubstrate having three standard silicon wafers 20 ₁, 20 ₂ and 20 ₃ whichare stacked and fusion bonded to one another. An example of thickness ofeach of the silicon wafers 20 ₁-20 ₃ is about 0.5 mm. The end of thecontactor 30 ₁ is protruded from the bottom surface of the contactsubstrate 20 for forming a contact pad 35. As an example, the size ofthe contact pad 35 is 0.5 mm in its width. The contactor 30 ₁ has aflange like portion 35 to be fitted with a step in the through hole 25.A contact point 31 ₁ at the tip of the contactor 30 ₁ is preferablysharpened to promote the scrubbing effect on the surface of the contacttarget.

[0109]FIG. 13 is a cross sectional view showing an example of contactstructure of the present invention using the contactors 302 producedthrough the process such as FIGS. 8A-8L, 9A-9D or 10A-10N. The contactor30 ₂ having the loop shape is attached to the contact substrate 20 in amanner that both ends of the contactor 302 are inserted in through holes25. Both ends or at least one end of the contactor 30 ₂ is projectedfrom the bottom surface of the contact substrate 20 for forming contactpads 35. As an example, the size of the contact pad 35 is 0.5 mm in itswidth. The contactor 30 ₂ has a flange like portion 35 to be fitted witha step provided in the through hole 25. A contact point 31 ₂ at the topcenter of the contactor 30 ₁ is preferably sharpened to promote thescrubbing effect on the surface of the contact target. The contactsubstrate 20 has the same structure as that shown in FIG. 12.

[0110] The process of forming three layered substrate 20 and throughholes thereon shown in FIGS. 12 and 13 is briefly explained in thefollowing. First, the second wafer 202 and the third wafer 20 ₃ aredirectly bonded through, for example, silicon fusion bonding. Then thewafers 20 ₂ and 203 ₃ are polished both front and back, and throughholes are created therethrough by an etching process. Such a deep trenchetching is achieved, for example, by reactive ion etching using areactive gas plasma. As shown in FIG. 11, the size of the through holeson the second and third wafers 20 ₂ and 20 ₃ must be smaller than theflange like portion 35 of the contactor 30 to form the steps in thethrough holes.

[0111] Then, the first wafer 20 ₁ is polished its front and backsurfaces and through holes 25 are created therethrough by the deeptrench etching noted above. The size of the through holes of the firstwafer 20 ₁ is larger than that of the second and third wafers 20 ₂ and20 ₃ to receive the flange like portion 35 of the contactor 30 as notedabove. The first wafer 20 ₁ is aligned and fusion bonded to the secondand third wafers 20 ₂ and 20 ₃. For insulation, silicon oxide layers of,for example, at least one micrometer is grown on all of the exposedsurfaces of the contact substrate produced in this manner. Then, thecontactor 30 is inserted in the through holes 25 and fixed therein by anadhesive.

[0112]FIG. 14 is a perspective view showing an example of contactstructure of the present invention having a large number of contactors30 produced through the process shown in FIGS. 8A-8L, 9A-9D or 10A-10Nand assembled in the manner shown in FIG. 14. This example shows aplurality of contactors 30 ₂ assembled in a single line, however, acontact structure of the present invention may include contactorsaligned in two or more lines, i.e, a matrix manner.

[0113]FIG. 15 is a cross sectional view showing an example of totalstack-up structure using the contact structure of the present inventionas an interface between a device under test (DUT) and a test head suchas shown in FIG. 2. In this example, the interface assembly includes aconductive elastomer 250, a routing board 260, and a pogo-pin block(frog ring) 130 provided over the contact structure in the order shownin FIG. 15.

[0114] The conductive elastomer 250, routing board 260 and pogo-pinblock 130 are mechanically as well as electronically connected with oneanother. Thus, electrical paths are created from the contact point 31 ofthe contactors 30 to the test head 100 through the cables 124 andperformance board 120 (FIG. 2). Thus, when the semiconductor wafer 300and the interface assembly are pressed with each other, electricalcommunication will be established between the DUT (contact pads 320 onthe wafer 300) and the test system.

[0115] The pogo-pin block (frog ring) 130 is equivalent to the one shownin FIG. 2 having a large number of pogo-pins to interface between theprobe card 260 and the performance board 120. At upper ends of thepogo-pins, cables 124 such as coaxial cables are connected to transmitsignals to printed circuit boards (pin electronics cards) 150 in thetest head 100 in FIG. 2 through the performance board 120. The routingboard 260 has a large number of electrodes 262 and 265 on the upper andlower surfaces thereof. The electrodes 262 and 265 are connected throughinterconnect traces 263 to fan-out the pitch of the contact structure tomeet the pitch of the pogo-pins in the pogo-pin block 130.

[0116] The conductive elastomer 250 is provided between the contactstructure and the probe card 260. The conductive elastomer 250 is toensure electrical communications between the contact pads 35 of thecontactors 30 ₁ and the electrodes 262 of the probe card by compensatingplanarization or vertical gaps therebetween. The conductive elastomer250 is an elastic sheet having a large number of conductive wires in avertical direction. For example, the conductive elastomer 250 iscomprised of a silicon rubber sheet and a multiple rows of metalfilaments. The metal filaments (wires) are provided in the verticaldirection of FIG. 13, i.e., orthogonal to the horizontal sheet of theconductive elastomer 250. An example of pitch between the metalfilaments is 0.05 mm with thickness of the silicon rubber sheet is 0.2mm. Such a conductive elastomer is produced by Shin-Etsu Polymer Co. Ltdand available in the market.

[0117] According to the present invention, the contact structure has avery high frequency bandwidth to meet the test requirements of nextgeneration semiconductor technology. Since the large number ofcontactors are produced at the same time on the substrate withoutinvolving manual handling, it is possible to achieve consistent quality,high reliability and long life in the contact performance. Further,because the contactors are assembled on the same substrate material asthat of the device under test, it is possible to compensate positionalerrors caused by temperature changes. Further, it is possible to producea large number of contactors in a horizontal direction on the siliconsubstrate by using relatively simple technique. Such contactors areremoved from the substrate and mounted on a contact substrate to form acontact structure such as a probe card in a vertical direction. Thecontact structure produced by the present invention is low cost and highefficiency and has high mechanical strength and reliability. The contactstructure produced by the method of the present invention areadvantageously applied in testing a semiconductor wafer, packaged LSI,multi-chip module and the like including burn-in testing.

[0118] Although only a preferred embodiment is specifically illustratedand described herein, it will be appreciated that many modifications andvariations of the present invention are possible in light of the aboveteachings and within the purview of the appended claims withoutdeparting the spirit and intended scope of the invention.

What is claimed is:
 1. A contact structure for establishing electricalconnection with contact targets, comprising: a contact substrate havingthrough holes; and a plurality of contactors where each of thecontactors has a hook shape and is comprised of a tip portion which isprotruded in a vertical direction to form a contact point, a baseportion which is inserted in a through hole provided on the contactsubstrate in such a way that an end of the contactor functions as acontact pad for electrical connection at a bottom surface of the contactsubstrate, and a curved portion provided between the tip portion and thebase portion which produces a contact force when the contactor ispressed against the contact target; wherein the end of the contactor isinserted in a through hole of the contact substrate to be projected fromthe bottom surface thereof to function as a contact pad for electricalcommunication with an external component.
 2. A contact structure forestablishing electrical connection with contact targets as defined inclaim 1, wherein the contact substrate is formed of a plurality ofsilicon wafers bonded to one another and the through holes on thecontact substrate are created through an etching process.
 3. A contactstructure for establishing electrical connection with contact targets asdefined in claim 1, wherein each of the contactors is provided with aflange like shape at the bottom portion thereof to be fitted in thethrough holes on the contact substrate.
 4. A contact structure forestablishing electrical connection with contact targets as defined inclaim 1, wherein the contact substrate is formed of first, second andthird silicon wafers, wherein the second and third silicon wafers arefusion bonded and a second through hole is created therethrough by anetching process, and a first through hole which is larger than thesecond through hole is produced on the first silicon wafer, and whereinthe first silicon wafer is aligned to match positions of the throughholes and fusion bonded to the second silicon wafer.
 5. A contactstructure for establishing electrical connection with contact targets,comprising: a contact substrate having through holes; and a plurality ofcontactors where each of the contactors has a loop shape and iscomprised of a center portion which is protruded in a vertical directionto form a contact point, a base portion having two ends, and a loopportion between the center portion and the base portion which ishorizontally curved to produce a contact force when the contactor ispressed against a contact target; wherein the two ends of the contactorare inserted in through holes provided on the contact substrate in sucha way that at least one end of the contactor is projected from a bottomsurface of the contact substrate to function as a contact pad forelectrical communication with an external component.
 6. A contactstructure for establishing electrical connection with contact targets asdefined in claim 5, wherein the contact substrate is formed of aplurality of silicon wafers bonded to one another and the through holeson the contact substrate are created through an etching process.
 7. Acontact structure for establishing electrical connection with contacttargets as defined in claim 5, wherein each of the contactors isprovided with a flange like shape at the bottom portion thereof to befitted in the through holes on the contact substrate.
 8. A contactstructure for establishing electrical connection with contact targets asdefined in claim 5, wherein the contact substrate is formed of first,second and third silicon wafers, wherein the second and third siliconwafers are fusion bonded and a second through hole is createdtherethrough by an etching process, and a first through hole which islarger than the second through hole is produced on the first siliconwafer, and wherein the first silicon wafer is aligned to match positionsof the through holes and fusion bonded to the second silicon wafer.
 9. Amethod for producing a contact structure, comprising the following stepsof: forming a sacrificial layer on a surface of a silicon substrate;forming an conductive layer made of electric conductive material on thesacrificial layer; forming a photoresist layer on the conductive layer;aligning a photo mask over the photoresist layer and exposing thephotoresist layer with ultraviolet light through the photo mask, thephoto mask including an image of the contactors; developing patterns ofthe image of the contactors on a surface of the photoresist layer;forming the contactors made of electric conductive material in thepatterns on the photoresist layer by an electroplating process;stripping the photoresist layer; removing the sacrificial layer and theconductive layer by an etching process so that the contactors areseparated from the silicon substrate; and mounting the contactors on acontact substrate having through holes to receive ends of the contactorstherein so that at least one end of each of the contactors functions asa contact pad for electric connection.
 10. A method for producing acontact structure as defined in claim 9, in the aligning and exposingstep, the photoresist layer is exposed by an electron beam or X-raysthrough the photo mask.
 11. A method for producing a contact structureas defined in claim 9, in the aligning and exposing step, thephotoresist layer is directly exposed by an electron beam, X-ray orlaser light to define the image of the contactor thereon.
 12. A methodfor producing a contact structure as def ined in claim 9, furtherincluding a step of forming an adhesion promoter layer between thesacrificial layer and the conductive layer.
 13. A method for producing acontact structure as defined in claim 9, wherein the electric conductivematerial for the conductive layer is different from the electricconductive material for the contactors.
 14. A method for producing acontact structure, comprising the following steps of: forming asacrificial layer on a surface of a silicon substrate; forming anconductive layer made of electric conductive material on the sacrificiallayer; forming a photoresist layer on the conductive layer; aligning aphoto mask over the photoresist layer and exposing the photoresist layerwith ultraviolet light through the photo mask, the photo mask includingan image of the contactors; developing patterns of the image of thecontactors on a surface of the photoresist layer; forming the contactorsmade of electric conductive material in the patterns on the photoresistlayer by an electroplating process; stripping the photoresist layer;placing an adhesive tape on the contactors so that upper surfaces of thecontactors adhere to the adhesive tape; removing the sacrificial layerand conductive layer by an etching process so that the contactors on theadhesive tape are separated from the silicon substrate; and mounting thecontactors on a contact substrate having through holes to receivetherein ends of the contactors wherein at least one end of each of thecontactors function as a pad for electric connection.
 15. A method forproducing a contact structure as defined in claim 14, in the aligningand exposing step, the photoresist layer is exposed by an electron beamor X-rays through the photo mask.
 16. A method for producing a contactstructure as defined in claim 14, in the aligning and exposing step, thephotoresist layer is directly exposed by an electron beam, X-ray orlaser light to define the image of the contact structure thereon.
 17. Amethod for producing a contact structure as defined in claim 14, furtherincluding a step of forming an adhesion promoter layer between thesacrificial layer and the conductive layer.
 18. A method for producing acontact structure as defined in claim 14, wherein the sacrificial layeris made of silicon dioxide.
 19. A method for producing contactstructures as defined in claim 14, wherein the electric conductivematerial for the conductive layer is different from the electricconductive material for the contactors.
 20. A method for producingcontact structures as defined in claim 17, wherein the adhesion promoterlayer is made of chromium (Cr) or titanium (Ti).
 21. A method forproducing a contact structure, comprising the following steps of: (a)forming an conductive substrate made of electric conductive material ona dielectric substrate; (b) forming a photoresist layer on theconductive substrate; (c) aligning a photo mask over the photoresistlayer and exposing the photoresist layer with ultraviolet light throughthe photo mask, the photo mask including an image of the contactors; (d)developing patterns of the image of the contactors on a surface of thephotoresist layer; (e) forming the contactors made of electricconductive material in the patterns on the photoresist layer by anelectroplating process; (f) stripping off the photoresist layer; (g)peeling the conductive substrate having contactors thereon from thedielectric substrate; (h) placing an adhesive tape on the contactors onthe conductive substrate so that upper surfaces of the contactors adhereto the adhesive tape wherein adhesive strength between the contactorsand the adhesive tape is larger than that between the contactors and theconductive substrate; (i) peeling the conductive substrate so that thecontactors on the adhesive tape are separated from the conductivesubstrate; and (j) mounting the contactor on a contact substrate havinga through hole in such a way the an end of the contactor is projectedfrom an opposite surface of the contact substrate.
 22. A method forproducing a contact structure as defined in claim 21, wherein theconductive substrate and the contactors are made of nickel-cobalt(NiCo).
 23. A method for producing a contact structure as defined inclaim 21, further comprising a step of forming a chrome-inconel layer onthe dielectric substrate where the conductive substrate is created onthe chrome-inconel layer.
 24. A method for producing a contact structurehaving contactors each of which is able to exhibit a spring force forestablishing electrical contact with a contact target, comprising thefollowing steps of: forming a sacrificial layer on a surface of asilicon substrate; forming an conductive layer made of electricconductive material on the sacrificial layer; forming the contactorsthrough a photolithography process, the contact structures being in ahorizontal directions on the silicon substrate; transferring thecontactors from the silicon substrate to an adhesive tape; positioningthe adhesive tape having the contactors in a predetermined location;picking the contactor from the adhesive tape and orienting the contactorin a predetermined direction; positioning a contact substrate havingthrough holes for receiving therein base portions of the contactors; andplacing the contactors on predetermined positions of the contactsubstrate by inserting ends of the contactors in such a way that atleast one end of each of the contactors functions as a contact pad forelectrical connection.